Field of the Invention
This invention relates generally to a waste oil burner, and more particularly, but not by way of limitation, to a liquid fuel combustion device specifically designed to utilize waste and contaminated used oils without the need for pre-processing or filtering the fuel stock. The device relates to the general category of liquid fuel burners that employ vortex flow conditions in the combustion zone.
Description of the Related Art
The prior art concerning liquid fuel burners includes many methods and combinations of those methods of introducing fuel vapor or small fuel droplets into a combustion air stream. These methods represent an effort to reduce fuel droplet size and increase mixing accuracy and homogeneity with the combustion air. Vaporization methods are limited to light fuel oils with a tightly controlled viscosity range for a specific burner type. Heavy fuels burners utilize some method of droplet generation and distribution. Since fuel droplets have a liquid volume and combustion occurs at the surface of the droplet, the surface area to volume ratio of the fuel droplet is critical for efficient combustion. Large droplet sizes take longer to completely burn and are difficult to retain in the combustion zone until completely burned. Smoke and soot formation result. The fuel droplet volume is proportional to the cube of its diameter and the droplet surface area is proportional to the square of the diameter therefor the smaller the droplet size the better. There are practical limitations for reducing droplet size, and the heavier the fuel the larger is the limiting size. Droplet size consistency is also critical and requires careful maintenance of high quality machinery. None of the current methods is well suited to fuels of variable quality and viscosity or wide ranges of viscosity. Nor are they suitable for contaminated or particulate laden waste fuels.
A summary of the types of fuel delivery and combustion air mixing methods includes: surface vaporization by combustion heat from the surface of a pool of fuel or a wick into a convection of forced air draft (suitable for light low viscosity fuels only), pressurized fuel spray through a nozzle directly into a forced or natural convection air stream, pressurized and preheated fuel sprayed through a nozzle directly into a forced or natural convection air stream, pressurized fuel sprayed through an atomizing nozzle utilizing high temperature steam or compressed air to tear apart the liquid oil and spray it into the air stream, and use of a centrifugal slinger to spread the fuel into a thin film before it flings off into the supplied air stream. All of these methods require their particular combination of tanks, pumps, filters, preheaters, nozzles, and blowers to service carefully shaped combustion chambers for their specific combustion characteristics. Achieving efficient combustion with these methods is typically a delicate balance requiring precise adjustments of the pressures, temperatures, and flow rates of the fuel and air. Frequently, specialized electronic controls are necessary to maintain proper combustion, or else frequent physical monitoring and manual adjustment are required. Air and combustion flow in the burners occupy a range from slow, linear and laminar to fast, cyclonic, and turbulent. Burners can incorporate a series of stages incorporating any of these flow regimes to achieve the desired combustion properties. Multiple stage combustion is produced by additional combustion airstreams admitted downstream from the primary combustion zone.
All of these variables are typically tailored to the particular heat production requirements for a particular fuel type in a particular environment in an effort to control emissions, combustion temperatures, heat output rate, and ash formation. The resulting high specificity and tightly restricted operating parameters of the designs makes them impractical or unsuitable for dealing with the variable nature of unprocessed waste fuel sources.
Based on the foregoing, it is desirable to provide a simple robust burner system to be fueled by any liquid based waste fuels in an as-is unprocessed state. This is purposed in order to achieve maximum economic value from waste liquid fuel stocks, and to safely eliminate environmental hazards that would be impractical to recycle or dispose of, thus rendering them an economic advantage.
It is further desirable to provide such a system with stable consistent combustion characteristics across the entire range of fuels and burn rates.
It is further desirable to provide simplicity of design and scalability incorporated throughout to produce a practical device. This is purposed in order to allow economical operation from small scale consumer applications to large scale industrial ones.
It is further desirable to provide robust design capable of durable long-life function in adverse conditions without need for adjustment, tuning, or technical support and maintenance.
It is further desirable to provide adjustable heat output rate to allow more efficient continuous operation tailored to the demand as compared to common full-on/full-off output regulation.
It is further desirable to provide separation of ash in small particle form from the flue gasses internal to the burner, continually collected in an ash reservoir, and self-cleaning operation.
It is further desirable to provide control of peak temperatures to prevent formation of nitrogen oxides.
It is further desirable to provide leakage safe positive pressure combustion coupled with low external operating temperatures for fire safety.
It is further desirable to provide fuel supplied at low pressure without preheating or filtration to allow use of particulate laden and slurried fuels.
It is further desirable to provide easy application to a wide variety of heating applications including furnaces, boilers, and industrial processes.